Zeisel determination
Encyclopedia
The Zeisel determination or Zeisel test is a chemical test
for the presence of esters or ethers in a chemical substance
. It is named after the Czech chemist Simon Zeisel (1854–1933). In a qualitative test a sample is first reacted with a mixture of acetic acid
and hydriodic acid in a test tube
. The ensuing reaction results in the cleavage of the ether or the ester into an alkyl iodide and respectively an alcohol
or an carboxylic acid
.
By heating this mixture, the gases are allowed to come into contact with a piece of paper higher up the test tube saturated with mercury(II) nitrate
. Any alkyl iodide present will give a reaction with the mercury compound to mercury(II) iodide
which has a red or yellow color.
The reaction can also be used used determine the number of methoxy
(-OCH3) groups, by distilling the iodomethane into a solution of silver nitrate
, which precipitates silver iodide
. By filtering and weighing this precipitate it is possible to calculate the number of iodine
atoms and hence methoxy groups.
Synthetic applications:
Chemical test
In chemistry, a chemical test is a qualitative or quantitative procedure designed to prove the existence of, or to quantify, a chemical compound or chemical group with the aid of a specific reagent...
for the presence of esters or ethers in a chemical substance
Chemical substance
In chemistry, a chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. They can be solids, liquids or gases.Chemical substances are...
. It is named after the Czech chemist Simon Zeisel (1854–1933). In a qualitative test a sample is first reacted with a mixture of acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
and hydriodic acid in a test tube
Test tube
A test tube, also known as a culture tube or sample tube, is a common piece of laboratory glassware consisting of a finger-like length of glass or clear plastic tubing, open at the top, usually with a rounded U-shaped bottom....
. The ensuing reaction results in the cleavage of the ether or the ester into an alkyl iodide and respectively an alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
or an carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
.
By heating this mixture, the gases are allowed to come into contact with a piece of paper higher up the test tube saturated with mercury(II) nitrate
Mercury(II) nitrate
Mercury nitrate is a toxic colorless or white soluble crystalline mercury salt of nitric acid. It was also used to treat fur to make felt in a process called 'carroting'. The phrase 'mad as a hatter' is associated with psychological illness brought on by excessive exposure to mercury nitrate...
. Any alkyl iodide present will give a reaction with the mercury compound to mercury(II) iodide
Mercury(II) iodide
Mercury iodide is a chemical compound with an appearance of red-orange crystals. Unlike mercury chloride it is hardly soluble in water Mercury(II) iodide (HgI2) is a chemical compound with an appearance of red-orange crystals. Unlike mercury(II) chloride it is hardly soluble in water Mercury(II)...
which has a red or yellow color.
The reaction can also be used used determine the number of methoxy
Methoxy
In chemistry , methoxy refers to the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula O–CH3.The word is used in organic nomenclature usually to describe an ether...
(-OCH3) groups, by distilling the iodomethane into a solution of silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...
, which precipitates silver iodide
Silver iodide
Silver iodide is a yellow, inorganic, photosensitive iodide of silver used in photography, in medicine as an antiseptic, and in rainmaking for cloud seeding.-Crystal structure:...
. By filtering and weighing this precipitate it is possible to calculate the number of iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
atoms and hence methoxy groups.
Synthetic applications: